The type of system that Ann refers too uses regular picture molding.  If you search the web for art hanging system or similar words you should be able to find it.  A similar system uses a rigid thin rod instead of the cable - I've hung on both systems, and I prefer the rods over the cables.  Dick Blick has the rod system in their big catalog. 

If your paintings are light, you might want to go ahead and just use small nails.  That's what I use in my home gallery.  most of my paintings are just three sizes - so when I take one down, I hang another that is the same size in it's place.  then I don't ever have to move the nails. 

Hi Marcia,   sorry can't help you there.  Unfortunately I haven't kept in touch with my artist freind and I have very limited hardware knowledge.  But I'm sure someone in here has some  (knowledge that is).  Sorry I couldn't be of much help.

Ann 

That's what I had in mind, but I wanted to know all the logistics, like what's the best molding, what hooks work best on the moulding, what do I use for cable?  That sort of stuff.  I'm pretty sheltered myself, you see.

 -Marcia

Hi mj,   I had an artist friend who had a gallery.  What she did to hang artwork was to put up a moulding along the top of the wall at the ceiling and hang the pieces with thin wire from the moulding.  So they would each hang from thier own single long wire,  at different heights.  It looked very nice,  like they were all on plum lines.   Although I have a feeling this is somthing that is typical.  I've led a sheltered life.  lol.

Ann